Meanwhile, a senior U.S. lawmaker said he planned to travel to North Korea next year to improve relations.

Rep. Tom Lantos, who is set to become chairman of the International Relations Committee when Democrats take control of the House next month, said he had no firm date set for his trip. But he anticipated going in the first part of 2007, provided progress is made at the suspended six-nation talks aimed at persuading North Korea to abandon its nuclear weapons programs in return for aid and security assurances.

"I believe that as visits to North Korea become more routine and more regular, we will be creating a climate of greater confidence, diminished distrust," said Lantos, who has traveled to the North twice before. "I see no merit in no dialogue."

Lantos told reporters he supports better relations with North Korea, "but not at the expense of prostituting our own principles."

"The nuclear issue will have to be resolved, our currency cannot be counterfeited and human rights conditions will have to improve," he said.

The Bush administration has insisted that talks with North Korea occur in the context of nuclear disarmament discussions involving the Koreas, Japan, the United States, Russia and China. Those talks have been stalled for more than a year, and lawmakers from both political parties have urged outside dialogue to break the deadlock.

The North recently agreed to return to the nuclear talks after conducting its first-ever nuclear test on Oct. 9. Last week, U.S. diplomats met their North Korean counterparts in Beijing, and State Department spokesman Sean McCormack said Friday that the administration was "still hopeful that we'll be able to have a round that convenes this year, within the next week or so."

Lantos said he thought that Assistant Secretary of State Christopher Hill, the top U.S. envoy at the talks, should visit Pyongyang, "not as an alternative to the six-party talks, but as a complement" to them.

The United States also announced Friday a series of sanctions against North Korea triggered by the official finding that it had triggered a nuclear device in the October test. Although the United States quickly decided Pyongyang had conducted a test, Bush signed an official presidential determination only Thursday.

With that determination, the United States was required to bar nuclear cooperation under the Atomic Energy Act and financial assistance under the Export-Import Bank. The United States provides neither to North Korea. The determination also requires a wide range of economic sanctions that already are in place.

The White House said the finding did not affect humanitarian aid.